1. Field of the Invention
This invention is directed to a starter system for an internal combustion engine, and more particularly to a system including a starter motor and a solenoid driven pinion gear retraction system for use on existing aircraft engines.
2. Description of the Related Art
The development of internal combustion engines for airplanes has tracked somewhat with the development of automobile engines. Early examples of both had no separate electrical system, relying exclusively on magnetos for spark generation and hand cranks in the case of automobiles or hand "propping" for airplanes, for starting. Separate, battery operated starting systems for automobiles were developed in the early part of the century, including crankshaft driven distributors and coil and gap spark systems, but, for reasons of safety, reliability, and weight considerations, airplanes continued to use magnetos for spark generation and hand propping for starting.
With the development of more powerful airplane engines and more efficient airframe designs, plus the need for more sophisticated, electrically driven instruments, separate electrical systems for airplanes were developed in the late 1920's and the 1930's. However, for most smaller general aviation airplanes, the addition of starters and generators still represented a weight penalty which could not be tolerated. This was especially true since the early iron core starter motors and generators with large copper windings were extremely heavy.
After World War II was over, the flying public demanded electric starting systems for even the smallest airplanes and many engines, such as the venerable Continental 0-200, which were previously hand-propped, were retrofitted with electric starters. However, in the case of the Continental 0-200 and others, most such starters were either equipped with hand-operated cable pinion gear extenders, or with sprage clutches which were placed in line with the pinion gears and which merely disengage the pinion gears from the starter reduction gear, meaning that the pinion gear was constantly turning when the engine was running. The resulting constant wear and tear on the pinion gears was considerable, resulting in a shortened effective gear life and consequent frequent expense.
With the recent veritable explosion in home-built and "kit" planes, interest in venerable engines such as the Continental 0-200 and others is very high. However, the archaic starter designs in such engines, including their excessive weight and the undue wear and tear resulting from constant gear engagement, has created a need for an improved starting system for existing Continental airplane engines.
While improved starter systems have been developed for other airplane engines, including virtually all Lycoming direct drive piston engines, these prior starter systems have incorporated the starter motor and a solenoid pinion gear retractor with actuating lever in a single reduction gear housing chamber, with the solenoid placed outboard of and in line with the starter motor. Referring to FIG. 3, note the arrangement of a starter motor 6' and a solenoid pinion gear retractor 7' in a single receptacle 4' within a reduction gear housing 3'. This arrangement creates a number of problems. For instance, carbon dust from the brushes of the starter motor 6' tends to enter the solenoid 7' via the receptacle 4', shortening solenoid life and interfering with the lever action. Also, placement of the solenoid 7' outboard of and approximately aligned with the motor 6', a configuration designed to minimize the induction of carbon dust into the solenoid, necessitates a much longer cantilever lever arm from the solenoid 7' to a pinion gear (not shown) than would be otherwise required. Finally, the placement of the solenoid 7' and the starter motor 6' in line with each other necessitates a bulkier, and therefor heavier reduction gear housing.
Accordingly, it is clear that a need exists for an improved starter system for existing airplane engines, such as the Continental 0-200 and similar engines. Such a starter system should have a reduction gear housing with separate receptacles for a starter motor and a solenoid operated pinion gear extender, should be lighter than existing starters, and should space the starter motor and solenoid on the housing such that a lighter housing and a shorter pinion gear actuating lever are required.